This keypad telephone encoder circuit was found in ancient American documentation. The components used are common and are not difficult to obtain.
This power control with SCR was found in Radio Electronics from April 1966. The components are...
Suggested by a 90s Radio Elecrtronics, this circuit is intended to supply mobile equipment of the time....
This circuit was found in a Popular Electronics from the 90s. The circuit with the 555 monitors the...